9.8 CVE-2021-28799

CISA Kev Catalog Privilege Escalation Buffer Overflow Path Traversal Used by Malware Used by Ransomware

An improper authorization vulnerability has been reported to affect QNAP NAS running HBS 3 (Hybrid Backup Sync. ) If exploited, the vulnerability allows remote attackers to log in to a device. This issue affects: QNAP Systems Inc. HBS 3 versions prior to v16.0.0415 on QTS 4.5.2; versions prior to v3.0.210412 on QTS 4.3.6; versions prior to v3.0.210411 on QTS 4.3.4; versions prior to v3.0.210411 on QTS 4.3.3; versions prior to v16.0.0419 on QuTS hero h4.5.1; versions prior to v16.0.0419 on QuTScloud c4.5.1~c4.5.4. This issue does not affect: QNAP Systems Inc. HBS 2 . QNAP Systems Inc. HBS 1.3 .
https://nvd.nist.gov/vuln/detail/CVE-2021-28799

References

security@qnapsecurity.com.tw

https://www.qnap.com/en/security-advisory/QSA-21-13 Vendor Advisory

CPE

cpe	start	end
Configuration 1
AND
cpe:2.3:a:qnap:hybrid_backup_sync::::::::		< 16.0.0415
Running on/with
cpe:2.3:a:qnap:qts:4.5.2:::::::*
Configuration 2
AND
cpe:2.3:a:qnap:hybrid_backup_sync::::::::		< 3.0.210412
Running on/with
cpe:2.3:o:qnap:qts:4.3.6:::::::*
Configuration 3
AND
cpe:2.3:a:qnap:hybrid_backup_sync::::::::		< 3.0.210411
Running on/with
cpe:2.3:a:qnap:qts:4.3.3:::::::*
cpe:2.3:a:qnap:qts:4.3.4:::::::*
Configuration 4
AND
cpe:2.3:a:qnap:hybrid_backup_sync::::::::		< 16.0.0419
Running on/with
cpe:2.3:o:qnap:quts_hero:h4.5.1:::::::*
Configuration 5
AND
cpe:2.3:a:qnap:hybrid_backup_sync::::::::		< 16.0.0419
Running on/with
cpe:2.3:o:qnap:qutscloud::::::::	>= c4.5.1	<= c4.5.4

REMEDIATION

EXPLOITS

Exploit-db.com

id	description	date
No known exploits

POC Github

Url
No known exploits

Other Nist (github, ...)

Url
No known exploits

CAPEC

Common Attack Pattern Enumerations and Classifications

id	description	severity
1	Accessing Functionality Not Properly Constrained by ACLs In applications, particularly web applications, access to functionality is mitigated by an authorization framework. This framework maps Access Control Lists (ACLs) to elements of the application's functionality; particularly URL's for web apps. In the case that the administrator failed to specify an ACL for a particular element, an attacker may be able to access it with impunity. An attacker with the ability to access functionality not properly constrained by ACLs can obtain sensitive information and possibly compromise the entire application. Such an attacker can access resources that must be available only to users at a higher privilege level, can access management sections of the application, or can run queries for data that they otherwise not supposed to. [Survey] The attacker surveys the target application, possibly as a valid and authenticated user [Identify Functionality] At each step, the attacker notes the resource or functionality access mechanism invoked upon performing specific actions [Iterate over access capabilities] Possibly as a valid user, the attacker then tries to access each of the noted access mechanisms directly in order to perform functions not constrained by the ACLs.	High
104	Cross Zone Scripting An attacker is able to cause a victim to load content into their web-browser that bypasses security zone controls and gain access to increased privileges to execute scripting code or other web objects such as unsigned ActiveX controls or applets. This is a privilege elevation attack targeted at zone-based web-browser security. [Find systems susceptible to the attack] Find systems that contain functionality that is accessed from both the internet zone and the local zone. There needs to be a way to supply input to that functionality from the internet zone and that original input needs to be used later on a page from a local zone. [Find the insertion point for the payload] The attacker first needs to find some system functionality or possibly another weakness in the system (e.g. susceptibility to cross site scripting) that would provide the attacker with a mechanism to deliver the payload (i.e. the code to be executed) to the user. The location from which this code is executed in the user's browser needs to be within the local machine zone. [Craft and inject the payload] Develop the payload to be executed in the higher privileged zone in the user's browser. Inject the payload and attempt to lure the victim (if possible) into executing the functionality which unleashes the payload.	High
127	Directory Indexing An adversary crafts a request to a target that results in the target listing/indexing the content of a directory as output. One common method of triggering directory contents as output is to construct a request containing a path that terminates in a directory name rather than a file name since many applications are configured to provide a list of the directory's contents when such a request is received. An adversary can use this to explore the directory tree on a target as well as learn the names of files. This can often end up revealing test files, backup files, temporary files, hidden files, configuration files, user accounts, script contents, as well as naming conventions, all of which can be used by an attacker to mount additional attacks. [Directory Discovery] Use a method, either manual, scripted, or automated to discover the directories on the server by making requests for directories that may possibly exist. During this phase the adversary is less concerned with whether a directory can be accessed or indexed and more focused on simply discovering what directories do exist on the target. [Iteratively explore directory/file structures] The adversary attempts to access the discovered directories that allow access and may attempt to bypass server or application level ACLs by using manual or automated methods [Read directories or files which are not intended for public viewing.] The adversary attempts to access the discovered directories that allow access and may attempt to bypass server or application level ACLs by using manual or automated methods	Medium
13	Subverting Environment Variable Values The adversary directly or indirectly modifies environment variables used by or controlling the target software. The adversary's goal is to cause the target software to deviate from its expected operation in a manner that benefits the adversary. [Probe target application] The adversary first probes the target application to determine important information about the target. This information could include types software used, software versions, what user input the application consumes, and so on. Most importantly, the adversary tries to determine what environment variables might be used by the underlying software, or even the application itself. [Find user-controlled environment variables] Using the information found by probing the application, the adversary attempts to manipulate any user-controlled environment variables they have found are being used by the application, or suspect are being used by the application, and observe the effects of these changes. If the adversary notices any significant changes to the application, they will know that a certain environment variable is important to the application behavior and indicates a possible attack vector. [Manipulate user-controlled environment variables] The adversary manipulates the found environment variable(s) to abuse the normal flow of processes or to gain access to privileged resources.	Very High
17	Using Malicious Files An attack of this type exploits a system's configuration that allows an adversary to either directly access an executable file, for example through shell access; or in a possible worst case allows an adversary to upload a file and then execute it. Web servers, ftp servers, and message oriented middleware systems which have many integration points are particularly vulnerable, because both the programmers and the administrators must be in synch regarding the interfaces and the correct privileges for each interface. [Determine File/Directory Configuration] The adversary looks for misconfigured files or directories on a system that might give executable access to an overly broad group of users. [Upload Malicious Files] If the adversary discovers a directory that has executable permissions, they will attempt to upload a malicious file to execute. [Execute Malicious File] The adversary either executes the uploaded malicious file, or executes an existing file that has been misconfigured to allow executable access to the adversary.	Very High
39	Manipulating Opaque Client-based Data Tokens In circumstances where an application holds important data client-side in tokens (cookies, URLs, data files, and so forth) that data can be manipulated. If client or server-side application components reinterpret that data as authentication tokens or data (such as store item pricing or wallet information) then even opaquely manipulating that data may bear fruit for an Attacker. In this pattern an attacker undermines the assumption that client side tokens have been adequately protected from tampering through use of encryption or obfuscation. [Enumerate information passed to client side] The attacker identifies the parameters used as part of tokens to take business or security decisions [Determine protection mechanism for opaque token] The attacker determines the protection mechanism used to protect the confidentiality and integrity of these data tokens. They may be obfuscated or a full blown encryption may be used. [Modify parameter/token values] Trying each parameter in turn, the attacker modifies the values [Cycle through values for each parameter.] Depending on the nature of the application, the attacker now cycles through values of each parameter and observes the effects of this modification in the data returned by the server	Medium
402	Bypassing ATA Password Security An adversary exploits a weakness in ATA security on a drive to gain access to the information the drive contains without supplying the proper credentials. ATA Security is often employed to protect hard disk information from unauthorized access. The mechanism requires the user to type in a password before the BIOS is allowed access to drive contents. Some implementations of ATA security will accept the ATA command to update the password without the user having authenticated with the BIOS. This occurs because the security mechanism assumes the user has first authenticated via the BIOS prior to sending commands to the drive. Various methods exist for exploiting this flaw, the most common being installing the ATA protected drive into a system lacking ATA security features (a.k.a. hot swapping). Once the drive is installed into the new system the BIOS can be used to reset the drive password.
45	Buffer Overflow via Symbolic Links This type of attack leverages the use of symbolic links to cause buffer overflows. An adversary can try to create or manipulate a symbolic link file such that its contents result in out of bounds data. When the target software processes the symbolic link file, it could potentially overflow internal buffers with insufficient bounds checking. [Identify target application] The adversary identifies a target application or program that might load in certain files to memory. [Find injection vector] The adversary identifies an injection vector to deliver the excessive content to the targeted application's buffer. [Craft overflow file content] The adversary crafts the content to be injected. If the intent is to simply cause the software to crash, the content need only consist of an excessive quantity of random data. If the intent is to leverage the overflow for execution of arbitrary code, the adversary crafts the payload in such a way that the overwritten return address is replaced with one of the adversary's choosing. [Overflow the buffer] Using the specially crafted file content, the adversary creates a symbolic link from the identified resource to the malicious file, causing a targeted buffer overflow attack.	High
5	Blue Boxing	Very High
51	Poison Web Service Registry SOA and Web Services often use a registry to perform look up, get schema information, and metadata about services. A poisoned registry can redirect (think phishing for servers) the service requester to a malicious service provider, provide incorrect information in schema or metadata, and delete information about service provider interfaces. [Find a target SOA or Web Service] The adversary must first indentify a target SOA or Web Service. [Determine desired outcome] Because poisoning a web service registry can have different outcomes, the adversary must decide how they wish to effect the webservice. [Determine if a malicious service needs to be created] If the adversary wishes to redirect requests or responses, they will need to create a malicious service to redirect to. [Poison Web Service Registry] Based on the desired outcome, poison the web service registry. This is done by altering the data at rest in the registry or uploading malicious content by spoofing a service provider.	Very High
59	Session Credential Falsification through Prediction This attack targets predictable session ID in order to gain privileges. The attacker can predict the session ID used during a transaction to perform spoofing and session hijacking. [Find Session IDs] The attacker interacts with the target host and finds that session IDs are used to authenticate users. [Characterize IDs] The attacker studies the characteristics of the session ID (size, format, etc.). As a results the attacker finds that legitimate session IDs are predictable. [Match issued IDs] The attacker brute forces different values of session ID and manages to predict a valid session ID. [Use matched Session ID] The attacker uses the falsified session ID to access the target system.	High
60	Reusing Session IDs (aka Session Replay) This attack targets the reuse of valid session ID to spoof the target system in order to gain privileges. The attacker tries to reuse a stolen session ID used previously during a transaction to perform spoofing and session hijacking. Another name for this type of attack is Session Replay. The attacker interacts with the target host and finds that session IDs are used to authenticate users. The attacker steals a session ID from a valid user. The attacker tries to use the stolen session ID to gain access to the system with the privileges of the session ID's original owner.	High
647	Collect Data from Registries An adversary exploits a weakness in authorization to gather system-specific data and sensitive information within a registry (e.g., Windows Registry, Mac plist). These contain information about the system configuration, software, operating system, and security. The adversary can leverage information gathered in order to carry out further attacks. [Gain logical access to system] An adversary must first gain logical access to the system it wants to gather registry information from, [Determine if the permissions are correct] Once logical access is gained, an adversary will determine if they have the proper permissions, or are authorized, to view registry information. If they do not, they will need to escalate privileges on the system through other means [Peruse registry for information] Once an adversary has access to a registry, they will gather all system-specific data and sensitive information that they deem useful. [Follow-up attack] Use any information or weaknesses found to carry out a follow-up attack	Medium
668	Key Negotiation of Bluetooth Attack (KNOB) An adversary can exploit a flaw in Bluetooth key negotiation allowing them to decrypt information sent between two devices communicating via Bluetooth. The adversary uses an Adversary in the Middle setup to modify packets sent between the two devices during the authentication process, specifically the entropy bits. Knowledge of the number of entropy bits will allow the attacker to easily decrypt information passing over the line of communication. [Discovery] Using an established Person in the Middle setup, search for Bluetooth devices beginning the authentication process. [Change the entropy bits] Upon recieving the initial key negotiation packet from the master, the adversary modifies the entropy bits requested to 1 to allow for easy decryption before it is forwarded. [Capture and decrypt data] Once the entropy of encryption is known, the adversary can capture data and then decrypt on their device.	High
76	Manipulating Web Input to File System Calls An attacker manipulates inputs to the target software which the target software passes to file system calls in the OS. The goal is to gain access to, and perhaps modify, areas of the file system that the target software did not intend to be accessible. [Fingerprinting of the operating system] In order to create a valid file injection, the attacker needs to know what the underlying OS is so that the proper file seperator is used. [Survey the Application to Identify User-controllable Inputs] The attacker surveys the target application to identify all user-controllable inputs, possibly as a valid and authenticated user [Vary inputs, looking for malicious results] Depending on whether the application being exploited is a remote or local one, the attacker crafts the appropriate malicious input containing the path of the targeted file or other file system control syntax to be passed to the application [Manipulate files accessible by the application] The attacker may steal information or directly manipulate files (delete, copy, flush, etc.)	Very High
77	Manipulating User-Controlled Variables This attack targets user controlled variables (DEBUG=1, PHP Globals, and So Forth). An adversary can override variables leveraging user-supplied, untrusted query variables directly used on the application server without any data sanitization. In extreme cases, the adversary can change variables controlling the business logic of the application. For instance, in languages like PHP, a number of poorly set default configurations may allow the user to override variables. [Probe target application] The adversary first probes the target application to determine important information about the target. This information could include types software used, software versions, what user input the application consumes, and so on. [Find user-controlled variables] Using the information found by probing the application, the adversary attempts to manipulate many user-controlled variables and observes the effects on the application. If the adversary notices any significant changes to the application, they will know that a certain variable is useful to the application. [Manipulate user-controlled variables] Once the adversary has found a user-controller variable(s) that is important to the application, they will manipulate it to change the normal behavior in a way that benefits the adversary.	Very High
87	Forceful Browsing An attacker employs forceful browsing (direct URL entry) to access portions of a website that are otherwise unreachable. Usually, a front controller or similar design pattern is employed to protect access to portions of a web application. Forceful browsing enables an attacker to access information, perform privileged operations and otherwise reach sections of the web application that have been improperly protected. [Spider] Using an automated tool, an attacker follows all public links on a web site. They record all the links they find. [Attempt well-known or guessable resource locations] Using an automated tool, an attacker requests a variety of well-known URLs that correspond to administrative, debugging, or other useful internal actions. They record all the positive responses from the server. [Use unauthorized resources] By visiting the unprotected resource, the attacker makes use of unauthorized functionality. [View unauthorized data] The attacker discovers and views unprotected sensitive data.	High

MITRE

Techniques

id	description
T1005	Data from Local System
T1012	Query Registry
T1083	File and Directory Discovery
T1134.001	Access Token Manipulation:Token Impersonation/Theft
T1550.004	Use Alternate Authentication Material:Web Session Cookie
T1552.002	Unsecured Credentials: Credentials in Registry
T1562.003	Impair Defenses:Impair Command History Logging
T1565.002	Data Manipulation: Transmitted Data Manipulation
T1574.005	Hijack Execution Flow: Executable Installer File Permissions Weakness
T1574.006	Hijack Execution Flow:Dynamic Linker Hijacking
T1574.007	Hijack Execution Flow:Path Interception by PATH Environment Variable
T1574.010	Hijack Execution Flow: ServicesFile Permissions Weakness
© 2022 The MITRE Corporation. This work is reproduced and distributed with the permission of The MITRE Corporation.

Mitigations

id	description
T1005	Data loss prevention can restrict access to sensitive data and detect sensitive data that is unencrypted.
T1134.001	An adversary must already have administrator level access on the local system to make full use of this technique; be sure to restrict users and accounts to the least privileges they require.
T1550.004	Configure browsers or tasks to regularly delete persistent cookies.
T1552.002	If it is necessary that software must store credentials in the Registry, then ensure the associated accounts have limited permissions so they cannot be abused if obtained by an adversary.
T1562.003	Make sure that the <code>HISTCONTROL</code> environment variable is set to “ignoredups” instead of “ignoreboth” or “ignorespace”.
T1565.002	Encrypt all important data flows to reduce the impact of tailored modifications on data in transit.
T1574.005	Limit privileges of user accounts and groups so that only authorized administrators can interact with service changes and service binary target path locations. Deny execution from user directories such as file download directories and temp directories where able.
T1574.006	When System Integrity Protection (SIP) is enabled in macOS, the aforementioned environment variables are ignored when executing protected binaries. Third-party applications can also leverage Apple’s Hardened Runtime, ensuring these environment variables are subject to imposed restrictions. Admins can add restrictions to applications by setting the setuid and/or setgid bits, use entitlements, or have a __RESTRICT segment in the Mach-O binary.
T1574.007	Ensure that proper permissions and directory access control are set to deny users the ability to write files to the top-level directory <code>C:</code> and system directories, such as <code>C:Windows</code>, to reduce places where malicious files could be placed for execution. Require that all executables be placed in write-protected directories.
T1574.010	Limit privileges of user accounts and groups so that only authorized administrators can interact with service changes and service binary target path locations. Deny execution from user directories such as file download directories and temp directories where able.
© 2022 The MITRE Corporation. Esta obra se reproduce y distribuye con el permiso de The MITRE Corporation.

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